Robles, 25, had been dating Isiah's mother, 19-year-old Tequaneishia McGuire, for about a year. He was not the father of Isiah, the family said. About four months ago, they said, the two moved in together and lived at 7336 Central Park Circle off Temple Terrace Highway.

Around 2 p.m. Wednesday, Tequaneishia left Isiah in Robles' care when she left for her shift at Boston Market.

At 8:11 p.m., deputies say, Robles called 911 to report the baby was unresponsive.

It was around 9:30 p.m. when Nicole McGuire first heard from Tequaneishia that Isiah was at the hospital. Her daughter said Robles called from the hospital, saying the baby was "acting funny" and "throwing up."

When the 36-year-old grandmother arrived at the ER, she sat next to Isiah, cooing his name as he lay under the warmth of a hospital heat lamp. One small bruise darkened the middle of his honey-skinned forehead.

"Doo-Doo Dumpling," she repeated. Isiah reached toward his grandma and grabbed her finger. Then, a nurse stepped in and asked the family to step out while she ran tests.

A few minutes later, Nicole McGuire heard a voice echo through the hospital: "Code blue pediatric."

"I knew it was him," she said.

When she confronted Robles in anger, a hospital employee stepped in to separate them.

About two months earlier, Nicole McGuire said, she noticed a small bruise under Isiah's eye. She asked about the mark. Tequaneishia, she said, told her it was probably from his frequent climbs and tumbles.

On Sunday, Isiah took his first steps. He was at his grandmother's house, clutching a pencil as if it were another hand, Nicole McGuire remembered. He had only started saying words. "Hey-yo," he said when he answered the phone.

Tequaneishia's family said they never trusted Robles. He would sit back at family functions, cool and stand-offish.

About the time the bruise appeared, Nicole McGuire decided to start keeping her grandson from Thursday through Sunday every week, instead of weekends only. She said she noticed that the normally friendly and precocious Isiah seemed to recoil whenever he was handed to Robles.

"He never took to him," she said Thursday. He would cry and turn back to her.

But Robles seemed to have an unexplained hold over her daughter, she said.

Tequaneishia, a wisp of a woman, declined on Thursday to talk about what had happened.

When she entered her mother's Tampa home, an aunt asked if she was okay. Tequaneishia sat quiet and solemn in the corner of the couch, her hands folded in her lap. She nodded to signal she was, but said nothing. A tear dropped from the corner of her eye.

"No," a woman in the next room said. "She's not okay,"

In conversation over the last year, Robles spoke about a daughter who died in 2008 at about 4 months old, Nicole McGuire said. He told her that police investigated the death, but cleared him and were looking at other people, she said.

On Thursday, Nicole McGuire said, Tequaneishia called the mother of the baby who died on Jan. 12, 2008. "There were similarities," McGuire said.

Tampa police confirmed few details about the 2008 incident.

Davis said police couldn't release the names of the infant or the 15-year-old mother because police had investigated the mother as a sex crime victim in connection with the infant death case. At the time, Davis said, she "wasn't forthcoming about her relationship with Robles," who was not the child's father.

On Thursday, as Robles passed his first day in jail on suicide watch, Hillsborough sheriff's spokesman J.D. Callaway announced a new charge against him. He said an autopsy revealed Isiah had been sexually assaulted.

Florida records show no prior criminal record for Robles.

Already awash in horrifying news, Nicole McGuire responded calmly to word of the new charge. She was already driving to the Medical Examiner's Office to view her grandson's body.

Only a few days ago she expected to be spending this very day planning a party for Isiah's first birthday, May 13.

This week was supposed to be about Sponge Bob, cake, family in abundance.

Instead, she was talking to undertakers and a reporter, discussing funeral costs and viewing a tiny, lifeless body she loved.

"He just needs to pay in the worst way possible," McGuire said of Robles. "Nothing can happen to bring that baby back."

Times news researcher John Martin and staff writer Robbyn Mitchell contributed to this report. Rebecca Catalanello can be reached at rcatalanello@sptimes.com or (813) 226-3383.